Code
P20E1
Generic
P — Powertrain
Exhaust Aftertreatment Fuel Pressure Sensor Circuit Intermittent/Erratic
Views:
UK: 35
EN: 54
RU: 30
AI status
Completed
Completed
100%
Causes
- Damaged, corroded or loose sensor connector or wiring (intermittent open/short)
- Faulty exhaust aftertreatment fuel pressure sensor
- Intermittent ground or reference voltage (5V) supply to the sensor
- Contamination, internal sensor failure, or moisture intrusion
- Intermittent pump or pressure transducer mechanical issue causing spikes
- ECU/module fault or internal input circuit problem
Symptoms
- Malfunction Indicator Lamp (MIL) or check engine light illuminated
- Aftertreatment/DEF dosing warnings, limited dosing or limp modes
- Poor aftertreatment performance, increased NOx or failed emissions tests
- Possible reduced engine power or restricted operation in some vehicles
- Inconsistent or erratic pressure readings in live data
What to check
- Read freeze-frame and complete DTC list with a scan tool; note runtime and conditions
- View live data for the exhaust aftertreatment fuel pressure sensor while key on and during engine operation
- Inspect sensor connector and wiring for corrosion, loose pins, chafing, or damage
- Perform a wiggle test on harness/connectors while monitoring live data for signal dropouts
- Backprobe sensor connector to verify reference voltage (typically ~5 V), sensor ground, and signal voltage
- Measure continuity/resistance from sensor pins to ECU to check for intermittent opens or shorts
Signal parameters
- Reference supply: typically a stable 5 V reference (verify with vehicle spec)
- Signal output: normally a proportional DC voltage (typical range ~0.5–4.5 V depending on pressure and sensor type)
- Ground: low resistance connection to chassis/ECU ground
- No abrupt voltage spikes, dropouts, or oscillations during normal operation
- Open-circuit: very high resistance or no signal; short-to-ground: ~0 V; short-to-battery: ~battery voltage
Diagnostic algorithm
- Retrieve code, freeze frame and relevant live data. Note operating conditions when fault set.
- Visually inspect the sensor, tubing/pressure line, connector and wiring for damage, corrosion or contamination.
- With key on (engine off), backprobe connector and verify reference voltage (≈5 V) and good ground. Record values.
- Start engine and monitor the sensor signal voltage while operating the dosing system or inducing pressure changes; watch for instability or dropouts.
- Perform a wiggle test of the harness/connector while monitoring live data to reproduce the intermittent behavior.
- Check continuity/resistance from sensor pins to ECU connector with harness disconnected; inspect for intermittent opens when flexing harness.
- Use an oscilloscope to capture transient spikes, noise or irregular waveform that a DVM may miss.
- If wiring and power/ground are good, substitute a known-good sensor (if available) or replace the sensor and retest.
- After repair, clear codes and perform a road/operational test to confirm the fault does not return.
- If fault persists with verified sensor and wiring, consider ECU/input module diagnosis or replacement per manufacturer procedures.
Likely causes
- Wiring harness or connector corrosion/damage near sensor (most common)
- Sensor element failing internally or suffering from contamination
- Poor ground or intermittent reference voltage at sensor
- Intermittent open/short between sensor and PCM
Fault status
Status
Intermittent/erratic signal detected from exhaust aftertreatment fuel pressure sensor circuit. Possible wiring, connector, sensor or module issue.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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